catagory shiping options

Hello,
I have a shipping question

My site is https://www.letterboxfriendly.co.uk, in it I have and master category “gift cards” a master category “gift boxes and a master category “packaging”. Products in these categories are also otherwise categorized in line with the normal functions of Zen cart.

I want to be able to

• Ship everything on the site free to the UK
• Charge one flat rate for EU delivery for gift cards and another flat rate for rest of world delivery
• Charge one flat rate for EU delivery for gift boxes and another flat rate for rest of world delivery
• If more than one box is purchased then the postage also needs to go up in each case.
• For the packaging category I only wish to sell to the UK.

I have figured out how to do all of this with Standard Zen cart shipping modules, using the weight (not ideal), but I have one problem, when I test it (as for example as US customer)and I order packaging and a gift box the system allows the transaction , whereas if I test and order for packaging alone it refuses the transaction (as it should)

Any thoughts here are certainly worth a drink!